The Great Western occurrence lies at the head of the south fork of McGuigan Creek, at approximately 1830 metres elevation. The occurrence is 600 metres east the former Washington mine (082KSW008).

Hostrocks, consisting of slates of the Triassic Slocan Group, are heavily slickensided and carbonaceous. A quartz porphyry dike lies above part of the lode. For a more detailed description of the local geology refer to the Monitor mine (082KSW004).

The Great Western lode consists of a strongly sheared, mineralized zone, roughly 60 centimetres wide. The lode strikes nearly south and dips 35 to 55 degrees west. Galena, sphalerite and pyrite form irregular shaped ore shoots in a gangue of quartz and siderite. In places, nearly 30 centimetres of clean galena were encountered yielding nearly 68 grams per tonne silver and 1 per cent lead (Geological Survey of Canada Memoir 184, page 49). A chip sample taken over 30 centimetres in 1927 yielded 0.68 gram per tonne gold, 298 grams per tonne silver, 10.9 per cent lead and 24.3 per cent zinc (Minister of Mines Annual Report 1927, page 274). A grab sample yielded 0.34 gram per tonne gold, 634 grams per tonne silver, 28.4 per cent lead and 19 per cent zinc (Minister of Mines Annual Report 1927, page 274).

Production records are incomplete for the Great Western occurrence. Thirty-three tonnes were on the dump in 1893 and nearly 40 tonnes were shipped to the Trail smelter in 1906. A small tonnage was mined in 1927. Records indicate 58 tonnes produced 172,684 grams silver, 19,038 kilograms lead and 12,204 kilograms zinc in 1930.